Official comment
I would first check that you ACTUALLY had free space on the drive. A lot of DJs I've worked with have simply dragged the contents of the drive to the trash and ejected the drive, assuming that it was now empty. If you don't empty the trash while the drive is connected to the computer, it doesn't actually make that space available. This is just one possibility as to why it didn't record.
Another would be that the drive is corrupted / damaged. Either way, reformatting before recording should provide you the peace-of-mind in having a functional drive with available space.